Method for operation of automated top head and stem guide assembly for coking drums

ABSTRACT

An automated top head cover and stem guide assembly adapted for covering a top opening in vertical vessels such as coking drums, and a method for remotely operating the assembly. The top head assembly includes a flanged connector unit attached pressure-tightly to a top flange opening of a coking drum and a top cover device including a cover unit pivotally attached to the flanged connector unit, so that the cover unit can be pivotally lifted and moved aside. A stem guide device is also pivotally attached to the top flange unit, so that a stem guide unit can be pivotally moved downwardly into place over the top flange unit opening, after a stem member is inserted into the vessel. Following coke removal from the drum, the stem member is withdrawn, the stem guide unit is pivotally moved upwardly, and the head cover unit is moved downwardly to cover the coking drum flanged unit. The invention also discloses method steps for operating the head cover and stem guide devices of the assembly.

This is a division, of application Ser. No. 07/312,186, filed Feb. 21,1989, now U.S. Pat. No. 5,092,963.

BACKGROUND OF INVENTION

This invention pertains to an automated top head and stem guide assemblyfor vertical vessels such as coking drums. It pertains particularly toan automated removable top head cover unit used in combination with aremovable stem guide unit, and to a method for remote removal andreplacement operation for these units attached onto the vessel top headflanged opening.

During operation of delayed coking drums for the coking of various heavyhydrocarbon materials in petroleum refinery operations, the resultingcoke is deposited progressively on the inner walls of the drum and whenfull must be periodically removed, usually at 36-48 hour intervals. Atypical decoking apparatus for such coking drums is disclosed by U.S.Pat. No. 4,611,613 to Kaplan. Such coke removal from coking drums isaccomplished through an opening in the lower end of thevertically-oriented drum after the coke is cut away hydraulically by adevice inserted through an opening in the coking drum top head. Removalof the large top head cover to permit inserting the cutting deviceusually accomplished manually by using hoisting equipment. However,because the coking drum operates at relatively high temperatures of500-900 degrees F., such removal of the hot coking drum top cover bymanual means is slow and somewhat hazardous, and is thereforeundesirable.

Various mechanical unheading devices for large containers have beendisclosed in the prior art. For example, U.S. Pat. No. 3,751,854 toHuwyler et al discloses a lifting and swing mechanism for a crucibletype furnace. Also, U.S. Pat. No. 3,944,472 to Lowe discloses apivotable device for removing top lids of coke ovens. However, theseprior art devices have been found to have serious deficiencies whenapplied to unheading the top heads of coking drums. Such deficienceshave now been advantageously overcome by the present invention.

SUMMARY OF INVENTION

This invention provides an automated top head and stem guide assemblywhich is adapted for remotely operated pivotal removal and replacementof a cover unit from on top of vertically oriented vessel such as acoking drum. The invention includes a flanged connector unit which isattachable onto a vessel top flanged opening, a top head cover device,and an automated stem guide device which are each pivotally attached tothe flanged connector unit, which flanged unit is attachedpressure-tightly to a top flange of the vessel such as with a cokingdrum. The invention also provides method for remotely removing the tophead cover unit of a coking drum vessel and replacing it with apivotable stem guide unit onto the top flanged opening of a coking drum.

The top head cover device consists of a flanged connector unit which isattachable pressure tightly onto the top flange of the vessel, a coverunit which is pivotally attached to the flanged connector unit at oneside of the flanged connector unit, and a transverse beam unit pivotallyattached onto the cover unit upper side and movably attached at each endonto dual threaded screws pivotally connected onto the flanged connectorunit. The transverse beam unit is vertically movable on said dualthreaded jack screws by an actuator motor and gear box means.

The stem guide device also includes the pivotally attached flangedconnector unit at a location opposite that of the top head cover unit.The stem guide unit includes a lower base plate member having a centralopening therein and the dual horizontally movable clamping parts whichare pivotally attached to the upper side of lower base plate. The stemguide unit is operated by a pivotable piston actuator means adapted forraising and lowering the stem guide unit relative to the flangedconnector unit. Operation of the pivotable top head cover unit issynchronized with operation of the pivotable stem guide unit, so thatthe vessel top head cover unit is first pivotally moved upwardly and toone side, after which a coke removal stem member is inserted into thevessel, and the pivotable stem guide unit is pivotally lowered onto theupper flanged opening of the flanged connector unit to guide the stemmember during coke removal from the coking drum. Following such use ofthe stem guide unit, it is pivotally moved upwardly to its initialposition, and the stem member is removed, the top head cover unit ispivotally moved downwardly and repositioned onto the vessel top flangedconnector unit, and pressure-tightly connected onto the flangedconnector unit.

Accordingly, this invention advantageously provides an improved top headcover unit and stem guide assembly for vertical vessels such as cokingdrums. The assembly is adapted for providing remote safe and reliableremoval and replacement of a coking drum top head cover for moreconvenient and rapid removal of coke deposits from the drum duringperiodic decoking operations.

BRIEF DESCRIPTION OF DRAWINGS

This invention will be further described by reference to the followingdrawings, in which:

FIG. 1 shows a large vertically-oriented vessel having a top head coverunit and stem guide unit assembly which are each pivotally attached to atop flanged connector unit, which is attached pressure-tightly onto thevessel;

FIG. 2 shows a vertical elevation view of the vessel including the tophead cover unit shown in closed position and the stem guide unitassembly shown in open position;

FIG. 3 shows an alternative elevation view of the top head cover unit asviewed from line 3--3 of FIG. 2;

FIG. 4 shows a plan view of the top head cover unit taken at line 4--4of FIG. 2;

FIG. 5 shows an elevation view of the stem guide unit pivotally attachedonto the vessel top flanged unit with the guide plate shown in itsclosed position; and

FIG. 6 shows a plan view of the stem guide unit, including the dualhorizontally movable clamp members, taken at line 6--6 of FIG. 5.

DESCRIPTION OF INVENTION

As is generally shown by the FIG. 1 drawing, a vertically orienteddelayed coking drum vessel 10 is supported by a suitable supportstructure 11. Such delayed coking drums 10 for use in petroleumrefineries are usually 15-25 ft. diameter and 50-100 ft. tall, and havea conical shaped lower portion 10a which extends to a lower flangedopening 13. A movable lower cover unit is pressure-tightly and removablyattached to the lower flange 13. The coke material depositedprogressively on the walls of the coking drum 10 during cokingoperations is removed from the drum periodically as needed by firstremoving the lower flange unit 14, removing a top head cover assembly16, and then hydraulically cutting the deposited coke from within thevessel. The coke falls through flanged opening 13 and a chute into arailcar or storage pit (not shown) for further use as desired.

The coking drum 10 has an upper head flange 15, and a top head assembly16 which is pressure-tightly and removably attached to the upper flange15 by a plurality of fasteners such as bolts 17. As shown by FIGS. 2 and3, the top head assembly 16 included a top flanged connector unit 18,which includes a conduit portion having a bore extending axiallytherethrough, is attached to the top head flanged 15 by a plurality ofbolts 17. Upper flange plate 18a of connector unit 18 usually has itsouter diameter smaller than that of lower flange plate 18b, however, theupper flange outer diameter can be made substantially equal to or largerthan that of lower flange 18b.

A top head cover unit 20, which has a thermal insulation layer 20aprovided on its lower side, is attached to upper flange 18a of connectorunit 18 by bolts 19. Cover unit 20 is pivotally attached at 21 onto asupport bracket 18c, which is rigidly attached onto the lower flange 18bof the flanged connector unit 18. After removing bolts 19, the top headcover unit 20 is movable upwardly from a first lower position in contactwith upper flange 18a of connector unit 18, by a lifting mechanism,which includes a transverse beam structure 22, which is rigidly attachedonto the upper side of the top head unit 20. Beam structure 22 is alsopivotally attached at a central point 23 to a transverse movable beamunit 24. The beam unit is vertically movable on dual jack screws 26 bymotor drive mechanism 28, which includes dual gear units 28a and 28blocated at each end of beam unit 24 and threadably connected about thejack screws 26. These dual gear units are driven by hydraulic motor 30,which is mounted on gear box 28a and drives the gears through aconnecting shaft 29 and suitable couplings.

The lower ends of the jack screws 26 are pivotally attached at 31 to thelower flange 18b of the flanged unit 18. By this arrangement, when thehydraulic motor 30 is actuated, it rotates the dual gear units 28a and28b so as to lift beams 24 and head cover unit 20 upwardly on the dualjack screws 26 to a second upper position. During lifting, jack screws26 together with head cover unit 20 will pivot at their respective pivotpoints 31 and 21 relative to flanged unit 18 to its upper position, asshown by the phantom lines in FIG. 2. The top cover unit 20 and the beamstructure 24 are also shown in a plan view by FIG. 4.

After the head cover unit 20 is pivotally removed upwardly above theflange unit 18, it is replaced by stem guide unit 32, which is shown inan upright open position in FIG. 2, and is shown in a closed positiononto flanged unit 18 in FIG. 5. This guide unit 32 is pivotally attachedat 33 onto bracket 18d of flange unit 18, and includes a base platemember 34 and a dual horizontally movable clamping parts 36 locatedabove and pivotally attached to the base plate member 34. The clampingparts 36a and 36b are each pivotally attached at 37 to the base platemember 34, so that the clamping parts are horizontally movable relativeto each other and are also horizontally movable relative to the baseplate member 34, as is further shown by FIG. 6.

The stem guide unit 32 is pivotally actuated by a hydraulic pistonactuator 38, the body of which is pivotally attached at 39 to lowerflange 18b by a lower bracket 40. The piston rod 38a of actuator 38 isalso pivotally attached at 41 to an upper bracket 42 which is rigidlyattached to base member 34 of guide unit 32. By this configuration,whenever the rod 38a of piston actuator 38 is extended upwardly, thestem guide unit 32 can be pivotally lowered onto the upper opening ofthe flanged connector unit 18. However, before the stem guide unit 32 ispivotally lowered onto the flanged unit 18, a coke removal stem member50 is first inserted vertically through the bore in the flanged unit 18and into the coking drum vessel 10 to facilitate removal of coke fromthe vessel. The stem guide unit 32 is then lowered into position ontounit 18, so that dual pivotable clamping parts 36a and 36b are closedabout the stem member 50, and serve to guide the stem within the centralopening 44 and split guide bushing 46.

After such coke removal from the vessel 10, dual clamping parts 36a and36b and split guide bushing 46 are opened from around the stem member50, and the stem guide unit 32 is pivoted upwardly to a substantiallyupright position by actuator 38. Then the stem member 50 is removed fromthe vessel 10. When desiring to return head cover unit 20 to itsoriginal lowered position on flanged connector unit 18, the operation ofhydraulic motor 30 is reversed so that the head cover unit is lowered onthe dual jack screws 26 while cover unit 20 is simultaneously pivoted atits pivot 21. After the cover unit 20 is lowered into position onflanged unit 18, the bolt fasteners 17 are replaced so that the cokingvessel 10 can be repressurized for further operation.

The correct sequence of operations, by which the head cover unit 20 ispivotally raised and lowered from flange unit 18 by beam unit 24 and theguide unit 32 is pivotally raised and lowered by piston actuator 38, iscontrolled by an interlock system (not shown). This interlock system isconnected both electrically and hydraulically by known switching meansto actuator motor 30 of beam unit 24, and also is connected to controlvalves (not shown) for actuator piston 38, so as to prevent anyinterference between the pivotal movements of the head cover unit 20 andguide unit 32.

This invention will be further described by the following example ofoperations, which should not be construed as limiting the scope of theinvention.

A large vertically oriented coking drum is equipped with an automatedtop head cover device. This device includes a flanged connector unitwhich has its lower flange bolted onto the top flange opening of thecoking drum.

A top cover unit is pivotally attached to flanged connector unit lowerflange, so as to cover the opening in the connector unit upper flange. Alifting mechanism is pivotally attached to the cover unit upper side,which mechanism is in the form of a transverse beam connected to dualjack screws which are pivotally attached onto the lower flange of theconnector unit. The transverse beam is operated by a hydraulic motorwhich drives dual gear boxes which engage the jack screws. A source ofpressurized hydraulic fluid is connected to the motor by flexible hosesextending from the fluid source. Thus, whenever it is desired to raisethe top cover to a pivoted upright position, the drive motor is actuatedso that the cover unit is lifted and simultaneously pivoted to theupright position.

Important construction parameters for the top cover device are providedbelow:

    ______________________________________                                        Vessel top flange diameter, in,                                                                           48                                                Connector conduit top flange diameter, in.                                                                30                                                Cover unit diameter, in.    36                                                Jack screw length, in.      60                                                Transverse beam unit length, in.                                                                          50                                                ______________________________________                                    

EXAMPLE 2

The coking drum described in Example 1 is also provided with a stemguide device, which includes a stem guide unit which is also pivotallyattached to the lower flange of the flanged connector unit at a locationdiametrically opposite the pivotal attachment point for the top coverunit. The stem guide unit is actuated by a hydraulic piston actuatorwhich has its body member pivotally attached at its upper end to theconnector unit lower flange, and has its piston rod pivotally attachedto the stem guide unit. The piston actuator is operated by a pressurizedhydraulic fluid provided through flexible hoses from a suitable fluidsource.

By this arrangement, the stem guide unit which is originally in anupright position is pivotally lowered down onto the top flange of theflanged connector unit around an elongated stem device which waspreviously inserted through the flanged connector unit into the vessel.Then the dual horizontally movable clamps are pivoted to their closedposition, so as to guide the vertical member during its operation.Following coke removal from the vessel, the stem guide unit is pivotallyraised to an upright position, and the stem device is removed from thevessel.

Important parameters for the stem guide device are tabulated below:

    ______________________________________                                        Guide unit outer diameter, in.                                                                            36                                                Sector angle for guide unit opening, deg.                                                                 45                                                Offguide unit clamps, opening diam. in.                                                                    8                                                ______________________________________                                    

Although this invention has been described broadly and in terms of apreferred embodiment, it will be understood that modification andvariations can be made to the invention which is defined by thefollowing claims.

What is claimed:
 1. A method of alternately opening and covering a topopening in a vertically-oriented vessel having a flanged connector unitattached to the top opening, including the steps of:(a) raising a tophead cover that is pivotally attached to said flanged connector unitfrom a position covering the top opening to a substantially uprightposition; (b) inserting a stem member through said flanged connectorunit and the top opening of the vessel; (c) lowering a stem guide unitthat is pivotally attached to said flanged connector unit from asubstantially upright position to a position over said top opening andaround said stem member; (d) raising said stem guide unit back to thesubstantially upright position; (e) withdrawing said stem member; and(f) lowering said top head cover over the top opening of thevertically-oriented vessel.
 2. The method of claim 1, including thefurther steps of moving together dual, horizontally movable clampmembers pivotally attached to the top of said stem guide unit so as toclamp the vertically-oriented stem member therebetween.
 3. The method ofclaim 1, including the further steps of actuating a transverse beam unitthat is pivotally attached to said top head cover and movably attachedto dual jack screws that are pivotally attached to said flangedconnector unit.
 4. The method of claim 3, including the further steps ofmoving together dual, horizontally movable clamp members pivotallyattached to the top of said stem guide unit so as to clamp thevertically-oriented stem member therebetween.